When light moves from a less dense medium into a denser medium, it is refracted ______ the normal.

When light moves from a less dense medium into a denser medium, it is refracted ______ the normal.

• A. Toward the normal
• B. Away from the normal
• C. Parallel to the normal
• D. Perpendicular to the normal

Answer: (A)

When light enters a denser medium, its speed slows and the path bends toward the line that is perpendicular to the surface (the normal). This bending toward the normal happens because the change in speed at the boundary requires the ray to adjust direction to satisfy Snell’s law: n1 sinθ1 = n2 sinθ2. Since the second medium has a higher refractive index (n2 > n1), the sine of the refracted angle sinθ2 must be smaller than sinθ1, so the refracted ray makes a smaller angle with the normal than the incident ray. In other words, θ2 is less than θ1, which means the ray is bent toward the normal. For reference, moving from a denser to a less dense medium would bend the ray away from the normal. The ray being parallel to the normal would only occur if the incidence angle were zero, and it would be perpendicular to the normal only in that same special case or not at all for a typical oblique incidence.

When light enters a denser medium, its speed slows and the path bends toward the line that is perpendicular to the surface (the normal). This bending toward the normal happens because the change in speed at the boundary requires the ray to adjust direction to satisfy Snell’s law: n1 sinθ1 = n2 sinθ2. Since the second medium has a higher refractive index (n2 > n1), the sine of the refracted angle sinθ2 must be smaller than sinθ1, so the refracted ray makes a smaller angle with the normal than the incident ray. In other words, θ2 is less than θ1, which means the ray is bent toward the normal.

For reference, moving from a denser to a less dense medium would bend the ray away from the normal. The ray being parallel to the normal would only occur if the incidence angle were zero, and it would be perpendicular to the normal only in that same special case or not at all for a typical oblique incidence.